Exception in thread "main" java.lang.NullPointerException

[yotamoo]

So, i am trying to build a simple database (array of Car type).
the code is quite simple but for some reason i keep getting the same error after running the program (compiling went through). so i have 3 classes:

class DataBase {
    
    private Car[] database = new Car[3];

    public DataBase() {
    for (int i=0; i<database.length; i++) {
        database[i].formatCar();
    }
    
    } 
    
    public void addCar(Car car1) {
    for (int i=0; i<database.length; i++) {
        if (database[i].getModel()=="empty") {
        database[i]=car1;
        }
    }
    } 

    public void printDataBase() {
    int i=0;
    while (i<database.length) {
        database[0].printCar();
        i=i+1;
    }
    
    }

}

class mainpage {

    public static void main (String[] args) {
    Car car1 = new Car();
    DataBase database1 = new DataBase();
    car1.setCar();
     database1.addCar(car1);
    database1.printDataBase();
    }

}

import java.util.*;

class Car {

    private String _model;
    private String _color;
    private int _year;
    private Scanner _input = new Scanner(System.in);

    public Car() {

    _model = "empty";
    _color = "empty";
    _year = 0;

    }

    public void setCar() {

    System.out.print("Enter model: ");
    _model = _input.next();
    System.out.print("Enter color: ");
    _color = _input.next();
    System.out.print("Enter year: ");
    _year = _input.nextInt();

    }

    public void formatCar() {
    _model = "empty";
    _color = "empty";
    _year = 0;
    }

    public String getModel() {
    String model=_model;
    return model;
    }

    public String getColor() {
    String color=_color;
    return color;
    }

    public int getYear() {
    int year=_year;
    return year;
    }

    public void printCar() {
    System.out.println("Model :"+_model);
    System.out.println("Color :"+_color);
    System.out.println("Year :"+_year);
    }


}

And the error i get:

yotam@main computer:~/Documents/java/newcar$ java mainpage 
Exception in thread "main" java.lang.NullPointerException
    at DataBase.<init>(DataBase.java:7)
    at mainpage.main(mainpage.java:5)
yotam@main computer:~/Documents/java/newcar$

i searched for possible reasons and i came across the possibility that the array wasn't initialized, but then i changed to constructor to set model and color to "empty" and year to 0.
so now i have no clue, need your help guys.
Thanks!